If I apply for NIW and EB1-OR together at the same
time, should I request two recommendation letters from the same person? or use
the original for one petition, and the copy for the other?

Answer:

You don't have to send any originals to the USCIS, but you have to be able
to present the originals on request. If you have just one set, you can keep
originals and send copies only.

The USCIS no longer routinely requires
submission of original documents or "certified copies." Instead,
ordinary photocopies of such documents will be acceptable for initial filing and
approval of petitions and applications.